Rupert Murdoch used his political influence and contacts at the highest levels to try to get Labour MPs and peers to back away from investigations into phone hacking at the News of the World, a former minister in Gordon Brown's government has told the Observer.

The ex-minister, who does not want to be named, says he is aware of evidence that Murdoch, the chairman of News Corporation, relayed messages to Brown last year via a third party, urging him to help take the political heat out of the row, which he felt was in danger of damaging his company.

Brown, who stepped down as prime minister after last May's general election defeat for Labour, has refused to comment on the claim, but has not denied it. It is believed that contacts were made before he left No 10. The minister said: "What I know is that Murdoch got in touch with a good friend who then got in touch with Brown. The intention was to get him to cool things down. That is what I was told."

Brown, who became increasingly concerned at allegations of phone hacking and asked the police to investigate, had claimed that he was a victim of hacking when chancellor. He made Murdoch's views known to a select few in the Labour party.

In January, it was revealed Brown had written at least one letter to the Metropolitan police over concerns that his phone was targeted when he was still at the Treasury.

Suggestions that Murdoch involved Tony Blair in a chain of phone calls that led to Brown have been denied by the former prime minister. A spokesman for Blair said the claim was "categorically untrue", adding "no such calls ever took place". The allegation will, however, add to concerns about the influence Murdoch wielded over key political figures at Westminster and in Downing Street.

It will also raise further questions over the decision by David Cameron to appoint Andy Coulson, a former NoW editor who resigned over phone hacking, as his director of communications.

A spokesman for News International, the paper's owner, rebuted the claim, saying: "This is total rubbish."

Labour leader Ed Miliband weighed in on the hacking scandal , saying it was important to establish who knew what about "criminal behaviour" – and when. "What we have seen is a serious admission of wrongdoing by News International," he said during a visit to Swindon. "We have now got to get to the bottom of any criminal behaviour, which is a matter for the police. We need to know who knew about these actions and when. We also need to know how far across the organisation knowledge of these actions went."

On Friday, News International issued a public apology to eight victims of phone hacking, including the actress Sienna Miller and Tessa Jowell, the former culture secretary in Tony Blair's government. It was the first time the company had admitted the practice was common at the News of the World.

However, questions remain over whether the victims will settle. Miller's solicitor, Mark Thomson, of law firm Atkins Thomson, said: "She is awaiting information and disclosure from the News of the World which has been ordered by the court and will consider her next steps once this is provided."

The Department for Culture, Media and Sport said a decision on the planned takeover of BSkyB by News Corp would not be influenced by the controversy. A spokesman said: "The culture secretary has to make a quasi-judicial decision about the impact of the proposed merger on media plurality issues alone. Legally the culture secretary cannot consider other factors as part of this process and under law phone hacking is not seen as relevant to media plurality."

The scandal has focused attention on senior executives at News International, including its chief executive Rebekah Brooks, formerly Wade. Former MP George Galloway, who said he had been shown proof his phone had been hacked, claimed the NoW's apology was a "cynical attempt to protect the company's chief executive Rebekah Wade … Wade delivered the statement on Friday which sought to put an end to the controversy. However, by attempting to limit the admission of liability to the two years between 2004 and 2006 – and by so doing effectively sacrificing two senior executives and former editor Andy Coulson – she appears to be trying to exculpate herself from the scandal."

The publicist Max Clifford, who brought a private case against NoW that ended with a reported £1m settlement, said the newspaper had been forced into the apology. "It's now acknowledged this was widespread at News International."